The present disclosure relates to a planetary gear mechanism for converting a slow rotational movement of a drive shaft into a rapid rotational movement of an output shaft, the planetary gear mechanism having, on a planetary gear carrier, a bearing arrangement for rotatably mounting a planetary gear, comprising at least two tapered roller bearings which are arranged spaced apart axially from one another between the planetary gear and the planetary gear carrier, the at least two tapered roller bearings in each case having an inner ring and an outer ring, and an intermediate ring for axially positioning the at least two tapered roller bearings on the planetary gear carrier being arranged on an outer circumferential face of the planetary gear carrier between the two inner rings, a collar for axially securing the planetary gear being formed, furthermore, on an inner circumferential face of the planetary gear between the two outer rings radially along the inner circumference of the planetary gear.
The field of application of the disclosure extends to planetary gear mechanisms as are present in the drive train of a wind power plant having a power output of at least 1 MW. Important features of planetary gear mechanisms of this type are, inter alia, the dimensions and the weight. In the configuration of the gear mechanism parts, in addition to the material selection and the structural aspects, the prevailing forces and torques which act on the planetary gear mechanism are also important. Planetary gear mechanisms of this type are subject to extraordinary loadings which are caused on account of the structural position and the non-uniformly changing collective loading.
A bearing arrangement for the rotatable mounting of a planetary gear on a planetary carrier is apparent from DE 10 2006 051 817 A1, having two tapered roller bearings which are arranged at an axial spacing from one another, at least one radial bearing being arranged between the tapered roller bearings, in order to increase the load-bearing capability of the bearing arrangement. The radial bearing which is arranged between the tapered roller bearings can be adjusted with regard to the bearing play and/or the bearing prestress, in order to distribute the load-bearing capability of the bearing arrangement uniformly. Furthermore, a radially inwardly pointing annular web is formed on the planetary gear, the radially inwardly pointing circumferential face of which annular web is supported on the radially outer circumferential face of the outer ring of the radial bearing. Further specifications or solutions to problems of the inwardly pointing annular web are not apparent from the document.
Furthermore, a planetary gear which is mounted rotatably on a planetary carrier of a planetary gear mechanism is apparent from EP 1 837 535 A1, the mounting having two tapered roller bearings which are situated at an axial spacing from one another and are positioned in an X-arrangement. A spacer ring is arranged between an inner ring of one tapered roller bearing and an inner ring of the other tapered roller bearing, which spacer ring is segmented in the circumferential direction and is a constituent part of a group of various spacer rings with different graded widths. The prestress in two-row tapered roller bearings is defined by the spacer ring, the width of which as a result is adapted precisely to the required conditions and to the desired bearing play and/or the desired bearing prestress.
Moreover, a gear mechanism unit for a wind turbine arrangement is apparent from EP 1 252 442 B1. Said gear mechanism unit comprises a planetary gear stage, in which a planetary gear is mounted rotatably on a planetary gear carrier by two bearings, the bearings being spaced apart axially with regard to the rotational axis of the planetary gear. The bearings are conical bearings which come into contact in a surface region of the planetary gear. A central, integrated planetary gear section which extends radially inward between the bearings which are spaced apart axially can be seen from FIG. 2b. 
It is apparent from the generally known prior art that securing rings can be used for securing a planetary gear axially. The disadvantage of said known solution is that securing rings are subject to axial wear. Furthermore, torques in the MN range act in planetary gear mechanisms for wind power plants, with the result that the structural selection of securing rings can be associated with further risks. In order to eliminate the problem of the wear-susceptible securing rings, solutions are known, furthermore, in which a wear-resistant collar is provided for axially securing the planetary gear, which collar bears on the end side against both bearings. The disadvantage of said known solution is that the bearing play of the tapered roller bearing can be adjusted only in a very complicated manner by material-removing processes or grinding processes.